A conventional automatic bread maker will now be described with reference to FIGS. 9 and 10. FIG. 9 is a block view showing the construction of main portions of the conventional automatic bread maker, and reference numeral 1 denotes a baking chamber, reference numeral 2 a heater constituting heating means, reference numeral 3 a bread baking vessel removably mounted within the baking chamber, reference numeral 4 a motor, reference numeral 5 a belt for transmitting the power of the motor 4, reference numeral 6 a kneading blade driven by the motor 4, reference numeral 7 a temperature detection means abutted against an outer surface of the baking chamber 1 so as to detect the temperature of the bread baking vessel 3 for the purpose of a process judgment and a temperature control, reference numeral 8 a lid, reference numeral 9 a yeast charging port for charging yeast therethrough, reference numeral 10 a solenoid operatively connected to a valve of the yeast charging port 9 so as to drop the yeast, reference numeral 11 a control means which includes a microcomputer, and is responsive to a signal from the temperature detection means 7 for controlling the heater 2, the motor 4 and the solenoid 10 so as to bake the bread, reference numeral 12 a display portion for displaying the condition and time of the operation, and reference numeral 13 an operating portion for instructing a menu, a course and the initiation of the cooking (preparation).
When the operating portion 13 is operated to start the cooking, the control means 11 selects one of a plurality of bread-making processes in accordance with the temperature detected by the temperature detection means 7, and subsequently controls loads of the heater 2, the motor 4 and the solenoid 10 in accordance with the selected bread-making process, thereby effecting the bread-making operation.
FIG. 10 is a diagram showing, as one example, the detection temperature of the temperature detection means 7 and the rate of energization of the heater 2 in the baking step of the conventional automatic bread maker. When the baking step is started, the control means 11 causes the heater 2 to be continuously energized. When the temperature within the baking chamber 1 rises, and the temperature reaches 100.degree. C., the control means 11 is responsive to the output of the temperature control means 7 to reduce the rate of energization of the heater 2 to 85%. Then, when the temperature reaches 150.degree., the control means 11 reduces the rate of energization of the heater 2 to 30%. Thereafter, in accordance with the output of the temperature detection means 7, a temperature feedback control is effected at the energization rate of 30% when the detected temperature is not less than 130.degree. C., and at the energization rate of 65% when the detected temperature is less than 130.degree. C., and the cooking is completed a predetermined time period (50 minutes) after the baking is started.
In such a conventional automatic bread maker, since the temperature detection means is abutted against the outer surface of the baking chamber, and is not in contact with the bread baking vessel, this temperature detection means can not accurately detect the temperature of the bread baking vessel, and therefore even if the temperature feedback control is effected during the baking in order to keep the temperature of the bread baking vessel constant, the temperature difference between the bread baking vessel and the temperature detection means is large because of the influence of the outside (ambient) temperature and overshoot, and if the time, at which a crest and a trough of a temperature ripple come, is shifted even slightly, the baking color is greatly varied, and there were occasions when though the baking color was set to a dark color, it became a light color, and in contrast, though the baking color was set to a light color, it became a dark color.